Folding tops for cabriolet vehicles are known in different design variants, and as a rule, close a roof opening which protrudes along the vehicle roof as far as into the rear region. The folding top is configured such that it may be moved via a top linkage between an open position and a closed position in such a way that the folding top is stowed in a rear-side storage space in the open position. The folding top comprises a top linkage with a multiplicity of links, bows and hoops. A top cover is supported by the top linkage, which top cover spans the vehicle interior space in the closed position. The top linkage also comprises a tensioning hoop, on which the top cover is fixed on the rear side at the lower end region and which tensions the top cover in the closed position. The tensioning hoop is held on a tensioning hoop kinematic system and may be adjusted via the latter between its functional tensioning position which corresponds to the closed position of the folding top and a stowage position. In the stowage position of the tensioning hoop, the folding top is situated in the open position.
At the beginning of the stowing movement, the tensioning hoop may be moved from its tensioning position into a released position. In the released position, the tensioning hoop is raised up to such an extent that the tension of the top cover is cancelled and a rear flap which lies on the rear-side storage space may be lifted up. A storm linkage serves to secure the tensioning hoop in the tensioning position, via which storm linkage the tensioning hoop is supported on a component of the top linkage when the folding top is closed.
The adjustment of the tensioning hoop between the tensioning position and the stowage position via the tensioning hoop kinematic system takes place as a coupled movement of the movement of the folding roof. To this end, the tensioning hoop kinematic system is coupled to the roof kinematic system. During a movement of the roof kinematic system, the tensioning hoop likewise performs an adjusting movement. Via the tensioning hoop kinematic system, the tensioning hoop is attached firstly to the vehicle body and secondly to the roof kinematic system.
European Patent Publication No. EP 0 749 859 A1 has disclosed a folding top for a cabriolet vehicle, which folding top has a top linkage with a main drive. Furthermore, a tensioning hoop kinematic system is provided which comprises an upper storm rod, a lower storm rod and a tensioning hoop. The tensioning hoop kinematic system is assigned a separate drive member, the drive member being mounted on the vehicle body side and being configured as a hydraulic cylinder. A drive movement of the hydraulic cylinder is achieved via a swing arm which is mounted in a pivotably movable manner on the main bearing of the top linkage and is connected via a toggle lever to a tensioning lever in such a way that the upper storm rod may be moved towards the roof skin or away from it by way of the tensioning lever in accordance with the movement of the drive piston. Here, the lower storm rod is mounted on the tensioning hoop in such a way, and the front storm rod is mounted on the top linkage in such a way, that the tensioning hoop kinematic system may be moved independently of the main drive.
A disadvantage of the known embodiment of the roof kinematic system is, however, that the hydraulic cylinder which is assigned to the tensioning hoop kinematic system has to be switched to pressureless during the adjusting movement of the vehicle roof. Furthermore, the movement sequence during opening and closing of the vehicle roof is kinematically indeterminate.